The Efficacy of Green Tea Chewing Gum on Gingival Inflammation.

STATEMENT OF THE PROBLEM
According to previous studies, the components of green tea extracts can inhibit the growth of a wide range of gram-pos-itive and -negative bacterial species and might be useful in controlling oral infections.


PURPOSE
The aim of this study was to determine the effect of green tea chewing gum on the rate of plaque and gingival inflammation in subjects with gingivitis.


MATERIALS AND METHOD
In this double-blind randomize controlled clinical trial, 45 patients with generalized marginal gingivitis were selected and divided into two groups of green tea (23) and placebo (22) chewing gum. The patients chewed two gums for 15 minutes daily for three weeks. Sulcus bleeding index (SBI) and approximal plaque index (API) were studied at the baseline, 7 and 21 days later. Saliva sampling was conducted before and after 21 days for evaluation of IL-1β. The results were analyzed and compared by using repeated measures ANOVA, paired t test, and independent two-sample t test (α=0.05).


RESULT
The results showed that chewing gum significantly affected the SBI and API (p< 0.001). Paired t test showed that the two groups were significantly different regarding the mean changes of SBI and API at different periods of 1-7, 1-21, and 7-21 (p< 0.001). Concerning IL-1β, the repeated measures ANOVA revealed that the effect of chewing gum was significant (p<0.001). Moreover, paired t-test represented no significant difference between the mean changes of IL-1β within 1-21 day (p= 0.086).


CONCLUSION
The green tea chewing gum improved the SBI and API and effectively reduced the level of IL-1β.


Introduction
During the recent century, a main advancement has been attained in utilizing the herbs such as tea in medicine. Generally, three types of tea including black tea, green tea and Oolong tea (a Chinese type of tea) are derived from a shrub named Camellia sinensis. Green tea has advantage to other types of tea because it is less influenced by the fermentation process and its compositions remain stable. Green tea is known as an anticancer and antioxidant compound. [1][2][3] Many properties of the green tea are related to a component called catechin whose anti-oxidation activity is very pronounced and acts much stronger than other antioxidants such as vitamins C and E. [4] In a study, [5] it was observed that the polyphenols of green tea like Epigallocatechin gallat (EGCG) acted against TNFα and IL-1β inflammatory mediators and reduced the production of inflammatory cytokines such as IL8, which had an important role in absorbing neutrophils to the inflammatory sites. A number of researches on the green tea demonstrated that it has an anti-bacterial property against gram-positive and gramnegative bacteria such as Prevotella intermedia and Prevotella nigrescens. It also prevents the binding of porphyromonas gingivalis (P. gingivalis) bacteria to oral mucosal cells. [4][5][6] In addition, the catechins of green tea have the esteric structure of galloy radial, epigallocatechin gallat, and gallocatechin gallate which are the polyphenols that prevent the production of toxic metabolites of P. gingivalis. [7] These compounds prevent the formation of biofilms that contain P. gingivalis and Fusobacterium nucleatum (F. nucleatum), as well as the binding of periodontopathogens; they also reduce periodontal destruction. [8][9] One of the most important properties of green tea polyphenols is their restrictive effect on oxidative reactions of reactive oxygen species (ROS). ROS include free radical derivatives of oxygen. Green tea reduces the secretion of lysosome by separating ROS from the transition metal ions and prevents Fenton reactions and/or catalyzing oxidation reactions of the other molecules. [10][11][12] Since there was no completely similar study concerning the impact of green tea as chewing gum on oral diseases and gingival inflammation, conducting such a study seemed to be necessary. The objective of this study was to demonstrate the effect of green tea chewing gum on the level of plaque, gingival bleeding, and inflammation after 21 days consumption in patients with gingivitis. As the inclusion criteria, the patients were suppos-ed to be cooperative enough and had not received any periodontal treatment in the recent past six months.

Materials and Method
Those who suffered from systemic and metabolic diseases, used medications that could influence the intervention (chewing gum), had less than 20 teeth, pregnant patients, and the smokers were excluded.
After initial examinations, the sulcus bleeding index (SBI) and approximal plaque index (API) were measured, salvia samples were collected, and the patients were divided into experimental (G, n=23) and control (P, n=22) groups. The patients in G group were given two green tea chewing gums each day and those in P group received two placebo chewing gums each day for 21 days. All clinical indices were measured at the beginning, day 7, and day 21. The patients were in- Aslani et al. [14] The green tea extract used in this survey contained 207.32 mg/g caffeine, 130 mg/g catechin, and 200.82 mg/g flavonoid. It should be noted that the rate of these elements was different in various areas.
Totally, the rate of green tea used into each green tea chewing gum was 120 mg. [14] The standard rate of green tea is 240-320 mg polyphenol or 100-750 mg green tea per day. [4,15] Before beginning the study, the patients were instructed to brush their teeth daily by using fluoride toothpaste. Seven days later, API and SBI were measured in all patients. to the total areas of measured values. [16] In order to measure the SBI, the buccal and lingual marginal gingival and distal and mesial surfaces of papillary gingiva of the total teeth were studied (four surfaces of each tooth). The SBI value was described 30 seconds after gently inserting a periodontal probe into the sulcus of gingiva. It was scored depending on the rate of bleeding. Finally, the SBI was obtained through dividing the number of points with bleeding by the total studied points. [17] In order to evaluate the IL-1β at the first and third session (21 days later), salvia samples were collected before breaking the fast at morning. Patients were asked to keep their mouth relaxed for 5 minutes and then spout into a glass. This saliva was utilized in order to measure IL-1β inflammatory factor (unstimulated method).
The patients were asked to use two chewing gums daily (each gum for 15 minutes, totally 30 minutes). The API and SBI were measured after 7 and 21 days. The IL-1β was measured again after 21 days. Data were analyzed using brief statistical indices including the mean, standard deviation (SD), repeated measures ANOVA, paired t test, and independent two-sample t test (α=0.05).

Results
In this study, 45 participants completed the study process. The indices were not significantly different between the groups at the baseline (p< 0.001). Table 1 shows the mean±SD of API, SBI, and IL-1β of the groups in days 1, 7, and 21. Repeated measures ANO-VA showed that the API was significantly affected by the chewing gum type (p≤ 0.001) ( Table 1). Table 2 and Figure 1 display the changes of mean± SD of different indices in the two groups over the given timespans.

API changes
The mean±SD of changes of API over the first 7 days   Figure 1).

Repeated measures ANOVA performed on IL-1β
showed that it was significantly affected by the chewing gum type (p=0.038). (Table 1 IL-1β is recognized as a pathologic and preinflammatory factor since its level increases in salvia and gingival crevicular fluid during the progression of gingivitis. The present study showed that using green tea lowered the level of IL-1β. This finding was consistent with the results found by Maruyama et al. [21] and Nakamura et al. [22] Oxidative stresses play an important role in the initiation and progressing of periodontal inflammation. Green tea catechins reduce oxidative stresses by decreasing the production of preinflammatory cytokines. The two aforementioned studies reported that the green tea catechins decreased the production of IL-1β in gingival tissue as a response to lipopolysaccharide. It suggests that the green tea cate-chin relieves the oxidative stress as a modifier of innate immunity system. [21][22] Kushiyama et al. noticed a reversed relation between consuming green tea and periodontal disease.
[23] Moghbel et al. concluded that green tea mouthwashes reduced the rate of anaerobes bacteria more than chemical mouthwashes; it also prevented halitosis and plaque formation. [24] The positive trend of plaque reduction in this study may be related to the antibacterial property of green tea polyphenols. Kaneko et al. [25] found that a 4-week mouthwash regimen with diluted catechin solution reduced halitosis and periodontal dis-

Conclusion
The results of this study indicate that applying green tea as a chewing gum improves plaque and bleeding indices and also reduces IL-1β which is a pro-inflammatory cytokine. Therefore, the green tea chewing gum may be a safe adjunct for treatment of gingival inflammation.